1. Field of the Invention
The present invention relates to electrical connectors, and more particularly to a reliable boardlock for securing and grounding a connector to its associated printed circuit board.
2. Description of the Prior Art
The known prior art relating to this invention includes two groups of United States Patents.
The first group includes U.S. Pat. Nos. 4,865,555; 4,842,552; 4,824,398; 4,679,883; and 4,512,618. The structure of the boardlock disclosed in these patents has a central axis and comprises a body symmetrical about the central axis and received in a corresponding recess of the connector housing in an interference fit. This type boardlock functions only as a locking means.
The second group includes U. S. Pat. Nos. 4,938,704; 4,857,017. As shown in FIG. 1, the basic structure of boardlock comprises a flat metal fixedly connected to the vertical portion of a housing flange and a pair of legs extending downwardly in the rear portion. This kind boardlock functions as not only a locking means but also a grounding means. In details, at the end of each leg an expansion part is formed as a claw at an angle of 90 degrees to the corresponding leg, by which the connector is held on the board as shown in FIG. 2. As the pair of legs are inserted into the aperture of the board, each claw confronts the lower edge of the aperture on the back surface so as to secure the connector to the board. Due to the upper edge of the claw being at a right angle to the side edge of the leg, upon inserting the connector legs into the aperture of the board there is a space occurring between the connector and the board if the thickness of the board is smaller than ordinary, so it is impossible for the claws to hold the connector firmly on the board. In contrast, the claws cannot go completely through the aperture of the board to abut against the back edge of the board if the board is thicker than ordinary. In other words, this type boardlock is not well adapted to secure a connector to printed circuit boards of different thickness. Furthermore, referring to the cross-sectional view shown in FIG. 3, there are only two points contact between the legs and the aperture, so there remains the possibility for the connector to swing back and forth perpendicular to the line including these two points. This disadvantage effects the reliability of electrical connection between the connector and the board. A modified boardlock as shown in FIG. 4 constitutes an improvement for fastening the connector to the board. An additional leg is laterally offset out of the plane of the other two legs and disposed on a center line extending medianly between the two other legs. As shown in the cross-sectional view of FIG. 5, a three-point contact is thus formed between the three legs of the boardlock and the aperture of the board so that greater reliability is obtained than is possible with the two-point contact of FIG. 2.
There are a number of disadvantages resulting from this type boardlock. Some of these include a lack of grounding effect, insufficient retention force, and inability to accommodate different thicknesses of PC board. That is, with this type boardlock the area of contact between each leg of the boardlock and the aperture of the board is insufficient for reliable stability even though there is a three-point contact. For the same reason, the grounding effect through these three points of contact is not sufficiently reliable. In addition, for the aforementioned reasons the claws of the leg being fixed in their dimensions, cannot penetrate through the aperture to abut against the back side of the board if the board is thicker than that of the design specification. In contrast, a space is formed between the board and the connector so that no substantial or reliable retention exists between the connector and the board if the board is thinner than that of the design specification. Insufficient engagement and retention effects reliability so that the connector is subject to being pulled up through the aperture during soldering, thus producing a defective connection. This also debilitates the grounding effect, and the shielding effect is incomplete, resulting in the reception of spurious signals.
Accordingly, one of the important objects of the invention is the provision of a connector member incorporating a boardlock that is adapted to accommodate boards of different thickness.
Another important object of the present invention is the incorporation into a connector member of means to enhance its grounding effect.
Yet another object of the invention is the provision of a boardlock that may be manufactured as one piece to reduce the cost, and which will function as both a locking means and a grounding means.
Still another object of the invention is the provision of a boardlock for a connector that increases the contact area between the boardlock and the board so as to stabilize the connector on the board when installed.
The invention possesses other objects and features of advantages, some of which with the foregoing will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described, since it may be embodied in various forms within the scope of the appended claims.